Figure 2. A) Scanning electron micr

Figure 2. A) Scanning electron microscopy (SEM) images of the microstructures of cold-sintered samples prepared at different acid concentrations and their bulk density values. Acid concentrations: left 2m, middle 4.6m, right 9m. The sintering temperature is 300℃. B) Representation of crystallized Zn+2 ions from solution to lattice sites for different acid concentrations. Acid concentrations: left 2m, middle 4.6m, right 9m. C) SEM image of the microstructure of a cold-sintered sample and its bulk density value. The sintering temperature is 120℃,and the concentration is 2m. D) Representation of crystallized Zn+2 ions from solution to lattice sites. The solvent is pure water (left) and 2m aqueous acetic acid (right). Key: Zn+2 ion on the surface (blue); oxygen atoms on the surface (pink); oxygen atoms around migrating zinc (red); hydrogen atoms (white); surface zinc atoms (gray). The same color scheme is used for all images. To increase visibility, larger versions of the images in (B) and (D) are given in the Supporting Information.